1. Field of the Invention
The present invention relates to the field of automatic transmissions for motor vehicles. More particularly, it pertains to a kinematic arrangement having simple planetary gearsets.
2. Description of the Prior Art
Planetary gearsets used in automatic transmissions are controlled to produce multiple gear ratios by selectively engaging and disengaging clutches, which driveably connect and release connections among gearset components, and by selectively engaging and disengaging hydraulically operated brakes, which hold gearset components against rotation, thereby providing a torsional reaction, and release them for rotation.
Generally as the number of speed ratios produced by the transmission increases, the number of clutches and brakes required to control the transmission increases. However, each open or disengaged clutch and brake reduces operating efficiency of the transmission by causing drag between friction plates of the assembly. This drag is produced by shear forces transmitted across a narrow space filled with transmission fluid between the friction plates. Drag increases as fluid viscosity increases and as fluid temperature decreases.